(1) Field of the Invention
The present invention relates to a technology for measuring the level of a battery used as a power source of a telephone set and for informing the user of this level.
(2) Description of the Prior Art
Most mobile phones are equipped with a battery level indicator. A battery level indicator measures the remaining charge (hereafter xe2x80x9clevelxe2x80x9d) of the battery used to power the phone and displays one of a plurality of notification levels, such as xe2x80x9chighxe2x80x9d, xe2x80x9clowxe2x80x9d or xe2x80x9cvery lowxe2x80x9d, on an LCD (Liquid Crystal Display) or other display means. On being informed of the present battery level in this way, the user can proceed to recharge the battery when necessary. As representative examples, lithium ion secondary cells, nickel hydroxide secondary cells and nickel-cadmium cells are used to power mobile phones.
Through microcomputer control, a battery level indicator samples the battery voltage at predetermined intervals and judges which of the notification levels corresponds to the average of the sampled voltages. The notification levels correspond to different ranges of voltages that are demarcated by threshold values. The judgment as to the appropriate notification level may be performed at 1.0-second intervals, while the average may be calculated for thirty sampled values that are obtained at 0.5-second intervals. An average value for the battery voltage is used to remove the effects of momentary fluctuations in battery voltage. Such fluctuations occur due to changes in the power consumed by the various transmission and reception circuits due to factors such as whether communication is taking place.
Assume that a mobile phone operates in one of two modes: standby mode and communication mode. When the mobile phone is investigated separately during standby mode and during communication mode, the current drawn from the battery can be seen to be low during standby mode but higher during communication mode. When a high current is drawn from the battery, there is a drop in the sampled battery voltage due to the internal resistance of the battery.
To remove the effects of the internal resistance of the battery and display the battery level correctly, the notification levels need to be associated with different voltage ranges (i.e. different threshold values need to be used) depending on whether the mobile phone is in standby mode or in communication mode.
FIG. 1 shows the threshold values for the sampled value of the battery voltage that are used for each notification level.
In the illustrated example, the battery level is shown as one of five notification levels.
In FIG. 1, different threshold values are also set for the same notification level depending on temperature. This drawing also shows the actual symbols used to display each notification level.
A conventional battery level indicator uses threshold values like those shown in FIG. 1 to determine which notification level corresponds to the average taken for the sampled battery voltages. The battery level indicator then has the corresponding notification level displayed on an LCD or the like.
A conventional battery level indicator considers any increase in the battery level that occurs when the battery is not being recharged to be unnatural, and is designed so that the notification level will not be switched to a higher battery level unless the battery is being recharged.
When determining the appropriate notification level, a conventional battery level indicator uses an average calculated for sampled values of the battery voltage. Unless special control is performed, there is the problem that a lower display value will be displayed immediately after the phone switches from communication mode to standby mode.
In more detail, when the mode switches in this way, the period during which the battery voltage is sampled will include both values measured during communication mode and values measured during standby mode. If the average of these values is compared with the threshold values used during standby mode, a lower display value will end up being displayed to the user.
This problem is caused by the sampled values measured during communication mode being lower than the sampled values measured during standby mode. This lowers the average of the sampled battery voltage. If this lowered average is compared with the thresholds used for determining the notification level in standby mode, the device will choose a notification level that represents a lower level than the actual level of the battery.
In a battery level indicator that is designed not to select a higher notification level unless the battery is being recharged, any switch that lowers the notification level cannot be reversed. This means that the notification level will continue to be displayed incorrectly, exacerbating the above problem.
The following describes one example of the above problem using specific values.
FIG. 2 shows the battery voltage before and after a mobile phone switches from communication mode to standby mode.
As shown in the drawing, the battery voltage is around 3.63V during communication mode and around 3.76V 10 seconds or so after the switch to standby mode. When five notification levels are provided for the case where the temperature is 6xc2x0 C. or above, the battery level will be displayed as level 4 during communication mode and will remain at level 4 after some time has passed following the switch to standby mode.
However, immediately after the switch to standby mode, such as one second after, the average for the sampled values of the battery voltage that have been obtained in the preceding fifteen seconds is a low value, such as around 3.64V, due to the presence of values measured during communication mode. If the same criteria are used to determine the notification level, level 2 will be selected. As a result, the display value will switch from level 4 to level 2 after the end of the communication. When the limitation that prevents the notification level from switching to a higher level is operational, the notification level 2 will continue to be displayed until the battery is recharged.
In view of the stated problem, it is an object of the present invention to provide a battery level indicating apparatus that determines a notification level using an average for sampled values of the battery voltage, like a conventional apparatus, but does not mistakenly underestimate the battery level after a switch from communication mode to standby mode.
The stated object can be achieved by a battery level indicating apparatus for indicating a level of a battery, which powers a telephone having a communication mode and a standby mode, as one of a plurality of notification levels, the battery level indicating apparatus including: a threshold information storing unit for storing threshold information for specifying a notification level from a voltage of the battery during the standby mode; a measuring unit for measuring the voltage of the battery at intervals each equal to a first period to produce voltage measurements; a correcting unit for adding a correction value to each voltage measurement produced by the measuring unit during the communication mode to convert the voltage measurements to values equivalent to voltage measurements produced during standby mode; an average calculating unit for calculating, at intervals each equal to a second period, an average for the voltage of the battery from a predetermined number of most recent voltage measurements produced by the measuring unit, wherein voltage measurements produced during the standby mode are used without correction and voltage measurements produced during the communication mode are used having first been corrected by the correcting unit; a level determining unit for determining, every time the average calculating unit calculates the average, a notification level from the average in accordance with the threshold information; and an indicating unit for indicating the notification level determined by the level determining unit to a user of the telephone.
Here, the xe2x80x9cpredetermined number of most recent voltage measurementsxe2x80x9d that are averaged by the average calculating unit refers to the most recent measured values of the battery voltage with respect to the point at which the average is calculated.
With the stated construction, the voltage measurements produced during the communication mode are corrected. This means that when the predetermined number of voltage measurements used for calculating the average include both voltage measurements produced during the communication mode and voltage measurements produced during the standby mode, the notification level can still be properly determined from threshold values that determine voltage ranges for the standby mode. Correcting voltage measurements in this way removes the effects of the relatively low voltage measurements produced during the communication mode on the calculated average. This prevents the notification level from being determined at an erroneously low level, and so prevents an erroneously low level from being displayed to the user.
Here, the indicating unit may display a symbol showing the notification level determined by the level determining unit.
The stated construction prevents an inappropriate notification level from being shown to the user.
Here, the threshold information may specify a notification level based on a combination of a temperature of the battery and the voltage of the battery; the battery level indicating apparatus may further include a temperature detecting unit for detecting the temperature of the battery, the correcting unit may specify the correction value for a present voltage measurement according to the present voltage measurement and the temperature detected by the temperature detecting unit; and the level determining unit may refer to the threshold information and determine the notification level from the average and the temperature detected by the temperature detecting unit.
The stated construction can determine and display the battery level having taken into account the differences in discharge characteristics of the battery at different temperatures.
Here, the average calculating unit may calculate the average at all times except for a predetermined period following a switch by the telephone from communication mode to standby mode.
By operating as described above, the battery level indicating apparatus can remove the effects of the recovery period (see FIG. 2) for the battery voltage following a switch from communication mode to standby mode.
Here, the indicating unit may indicate the notification level determined by the level determining unit only when the determined notification level is equal to or lower than a notification level that is already being indicated by the indicating unit.
The stated construction prevents the battery level indicating apparatus from giving an unnatural display where the battery level rises.
The stated object of the present invention can also be achieved by a battery level indicating apparatus for indicating a level of a battery, which powers a telephone having a first mode and a second mode where different levels of current are drawn from the battery, as one of a plurality of discrete notification levels, the battery level indicating apparatus including: a threshold information storing unit for storing threshold information which is used for specifying a notification level from a voltage of the battery during the first mode; a measuring unit for measuring a voltage of the battery at intervals each equal to a first period to produce a voltage measurement; a correcting unit for correcting every voltage measurement produced by the measuring unit during the second mode by adding or subtracting a correction value to convert the voltage measurement to a value equivalent to a voltage measurement produced during the first mode; an average calculating unit for calculating, at intervals each equal to a second period, an average for the voltage of the battery from a predetermined number of most recent voltage measurements produced by the measuring unit, wherein voltage measurements produced during the first mode are used without correction and voltage measurements produced during the second mode are used having first been corrected by the correcting unit; a level determining unit for determining, every time the average calculating unit calculates the average, a notification level from the average in accordance with the threshold information; and an indicating unit for indicating the notification level determined by the level determining unit to a user of the telephone.
With the stated construction, the voltage measurements produced during the second mode are corrected. This means that when the predetermined number of voltage measurements used for calculating the average include both voltage measurements produced during the first mode and voltage measurements produced during the second mode, the notification level can still be properly determined from threshold values that determine voltage ranges for the first mode. This means that the notification level can be properly determined following a switch from the second mode to the first mode.
The stated object of the present invention can also be achieved by a battery level indicating apparatus for indicating a battery level of a battery, which powers a mobile phone having a communication mode and a standby mode, as one of a plurality of notification levels, the battery level indicating apparatus including: a memory for storing (1) a correction value table associating, for different temperature ranges, voltage values obtained during the communication mode with correction values for converting the voltage values obtained during the communication mode to values equivalent to voltage values obtained during the standby mode, and (2) a level table for specifying a notification level based on a combination of a temperature of the battery and the voltage of the battery; a temperature sensor for detecting the temperature of the battery; a measuring unit for measuring the voltage of the battery at intervals each equal to a first period to produce voltage measurements; a correcting unit for referring to the correction value table and specifying a correction value for each voltage measurement produced by the measuring unit during the communication mode based on the voltage measurement and the temperature detected by the temperature sensor, and adding the specified correction value to the voltage measurement; an average calculating unit for calculating, at intervals each equal to a second period, an average for the voltage of the battery from a predetermined number of most recent voltage measurements produced by the measuring unit, wherein voltage measurements produced during the standby mode are used without correction and voltage measurements produced during the communication mode are used having first been corrected by the correcting unit; a level determining unit for referring, every time the average calculating unit calculates the average, to the level table and determining a notification level using the calculated average and the temperature detected by the temperature sensor; and a liquid crystal display for displaying a symbol that represents the notification level determined by the level determining unit.
With the stated construction, the voltage of the battery that powers a mobile phone is measured and measurements made during the communication mode are corrected. This means that when voltage measurements used for calculating the average include both voltage measurements produced during the communication mode and voltage measurements produced during the standby mode, the notification level can still be properly determined from threshold values that determine voltage ranges for the standby mode. Correcting of voltage measurements in this way removes the effects of the relatively low voltage measurements produced during the communication mode on the calculated average. This prevents the notification level from being determined at an erroneously low level, and so prevents an erroneously low level from being displayed to the user.